Done right, a good science experiment is simple, clear and revealing. Done splendidly, it's a tale you don't forget. Let's do the sex one first. It took place in Italy, in the 1760s, when a Catholic priest and scholar, Lazzaro Spallanzani, was thinking about sperm — which is why he decided to dress frogs in pants, like this ...

That's right, pants. Spallanzani was a serious natural philosopher (what we'd now call a scientist); he was also very suspicious of a notion common in his day: that life sometimes spontaneously generates from nonlife.

People noticed that when meat was left on a table for long enough, baby flies appeared. The beef, it was said, birthed the flies. No one knew how. It just happened — poof! Decomposition — even of inorganic things — was key. Put some wheat husks on the ground, mix them with odoriferous human underwear, wait 21 days, and the sweat and the wheat would combine to generate (spontaneously) a mouse. This was a common belief.

Spallanzani thought otherwise. He believed that, in higher animals, not only was an egg necessary, but sperm was also required. He believed that life came only from life, not nonlife. Scholars had seen sperm, those wiggly things produced by the sex organ in a flush of solution. Obviously the spermy suspension had some purpose ...

... but what? So Spallanzani came up with this test.

He acquired a bunch of frogs, males and females. He separated them, and then, for the males, he designed what historians describe as "tight taffeta pants." I'm not sure exactly what they looked like. In some translations, the Italian reads as "short pants," so they might have looked like this ...

Or maybe like this ...

The pants were then fitted on the males, who, now dressed, were released. Their job, Spallanzani wrote, was to "seek [a] female with equal eagerness and perform, as well as they can, the act of generation."

But with pants on, it wasn't easy.

They got excited, with released sperm staining their garments, but the heavier, wiggly spermatozoa didn't get through.

Spallanzani, of course, had a control group (naked frogs who showered the eggs), and those eggs quickly began to develop, eventually producing tadpoles. But the bepanted frogs?

They begat no children. The tight pants had clearly removed a key ingredient. Sperm, it seemed, was necessary in these unions. Tadpoles, clearly, didn't spontaneously generate (and didn't, as another group thought, grow from teeny premade versions of themselves). No, Spallanzani proved that baby frogs come from two parents; and while he didn't get the mechanics exactly right, and while he went a little overboard fashionwise with his pant-sized Trojans — Spallanzani had made a major discovery.

To this day, there is a statue in Scandiano, Italy, of Spallanzani holding a magnifying glass in one hand and a frog in the other. The frog, I'm sorry to say, is not wearing pants. Spallanzani is, but you'd expect that. If it had been my sculpture, that frog would have been dressed. I think a teaching moment was missed here, big time. "Mama," I can hear kids all over town asking, "Perché quella rana porta i pantaloni (Why is that frog wearing pants)?" "Ummm," the mother would say, "ask your father."

The second experiment (which I'll get to in my next post) features John James Audubon — the great American bird illustrator — and some colleagues, who prepared a delicious lunch for vultures one day. It was a dead sheep, pre-opened and ready for eating. Only this particular sheep wasn't edible. That's because it was a drawing — a drawing sitting on top of real meat. Come back, and I'll explain what happened and why.